Iron filings burn vigorously due to their fine particle size, enhancing reactivity with oxygen. Copper, when heated, does not burn, but it forms a black-colored layer of copper(II) oxide on its surface.
Why do iron filings burn vigorously when sprinkled in the flame of a burner, and what happens to copper when heated?
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Iron filings burn vigorously when sprinkled in the flame of a burner due to the combustion of finely divided iron. The increased surface area of the filings promotes rapid oxidation, combining with oxygen in the air to form iron oxide (rust) with the release of energy.
When copper is heated, it undergoes a color change. Initially, it has a metallic pinkish hue, but as it gets hotter, it turns to a reddish color, eventually developing a dark brown or black coating. This change is due to the formation of copper oxide on the surface, indicating the reaction of copper with oxygen in the air (oxidation).